On Thursday, French Foreign Minister Laurent Fabius offered what is perhaps the most vehement reaction so far to opposition allegations that the regime of Syrian President Bashar Assad used chemical-warfare agents against civilians in the eastern suburbs around Damascus. If the use of such weapons is confirmed, Fabius told French broadcaster BFM, “France’s position is that there must be a reaction, a reaction that could take the form of a reaction with force.”

Fabius didn’t elaborate what, exactly, he meant by “force,” though he did rule out ground troops. “I believe [such an attack] cannot go without a reaction from those who believe in international legality.” The threat of applying “force” without deploying ground troops is an ambiguous one — all the more appropriate considering that everything that is known about the alleged attack is similarly ambiguous, from the number of dead to the chemicals used to how they might have been deployed to who might be responsible. And despite the fact that U.N. chemical-weapons inspectors are staying in a hotel not 5 km from the site of the alleged attack, the truth may never come out.

Here’s a breakdown of what we know, what we don’t know, and what we can’t know about what happened near Damascus on Aug. 21.

1. Method of deployment

Opposition activists reported a series of missiles launched at the area just before dawn. Videos that can’t be confirmed show a missile arc above the sky and a gray cloud above the area. Later footage showed exploded munitions that were purported to have caused the attack. In a blog post, Syrian weapons expert Brown Moses writes that he has seen similar, apparently Syrian-made, munitions linked to other alleged chemical attacks. Despite the possibly explosive nature of the munitions, none of the victims that appear in the videos seem to have been hit by shrapnel or explosives. Then again, they did hit early in the morning, so it’s possible no one was near the point of impact. Weapons inspectors would have to examine the munitions to determine if they carried chemical agents.

2. Location

Activists have posted a map listing the nine locations hit and casualty figures for each site. The figures have not been updated for 24 hours, but the locations are consistent with other tweets and videos.

3. The number of dead

Photos show scores, if not more, of dead, shrouded bodies lined up to be collected by family. Casualty counts range from low hundreds to 1,400, according to activists. But without cross-checking names with living relatives, it’s impossible to confirm any numbers at all. This will take time. The Syrian Observatory for Human Rights provides the most reliable casualty counts for the Syrian war based on extensive cross-checking; so far it has not been able to contribute a number for yesterday’s attack. Watch that space.

Video footage coming from the attack sites reveals a horrifying litany of symptoms, from vomiting, difficulty breathing, catatonic states, paralysis, foaming at the mouth, dilated pupils, constricted pupils, tremors, excess salivation and uncontrolled defecation and urination. These could all be symptoms of chemical attack, but they are inconsistent. Nerve agents like sarin, for example, don’t cause foaming at the mouth, but other lung irritants like chlorine gas might. Age, allergies and asthma can also impact how symptoms manifest. The agents in question could be diluted or combined in novel ways that produce an unusual array of symptoms. Even if the videos are unconfirmed, they clearly demonstrate that the victims are suffering horribly and that something terrible has happened to a large number of people. The only way to know for sure what kind of agents were used would be through testing blood and tissue samples of the victims, and environmental samples taken at the site.

5. Who is at fault?

This may never be known. Accusations are levied at all sides — the regime, the rebels, rogue elements of the government army, al-Qaeda-linked elements with the rebels. The list goes on. U.N. Secretary-General Ban Ki-moon said in a statement Thursday that the attack should be investigated without any further delay, and he dispatched a deputy, Under Secretary-General Angela Kane, to Damascus. Russia, the Assad regime’s biggest backer, also pushed for an investigation. Even if the U.N. chemical-weapons inspectors do gain access to the site, they will only be able to ascertain that chemical weapons were used. They will not be able to apportion blame, as it is not part of their mandate. Foreign intelligence agencies may come up with their own evidence, as the U.S., France and Israel have for past alleged attacks, but the nature of such evidence, and how it is obtained, is likely to mean that it will never be made publicly available. In the wake of the Iraqi WMD scandal, such information will always be suspect and tainted with allegations of political bias.

6. Reactions

About the only thing that can be counted on is the reaction of the international community. While condemnation has been swift, it is consistently couched with the cautious caveat of “if confirmed …” Barring a confession from one of the parties, such a confirmation may never be forthcoming, and French Foreign Minister Fabius may never have to explain, exactly, what he means by “force” without ground troops.

Aryn Baker is the Middle East Bureau Chief for TIME, covering politics, society, culture, religion, the arts and the military in the greater Middle East, including Pakistan and Afghanistan. She currently resides in Beirut, Lebanon.